Prostaglandins (PGs) play an important role in the implantation of the blastocyst in the uterus. Blastocysts contain large amounts of PGs in the blastococlic fluid just prior to implantation and release them readily in in vitro culture. The specific aims of the present proposal are to delineate more specifically the biochemical events in which PGs are involved in the interaction between the blastocyst and the uterus. Both biochemical and morphological studies will be made of the binding, uptake, release and exchange of PGs. Experiments will also determine the extent of synthesis and catabolism of PGs. The tissues to be used will be endometrium, myometrium and blastocysts, mainly as isolated cell preparations, so that each cell type can be studied separately. More information about this process which is crucial to successful reproduction will enable us to develop more effective and specific contraceptive methods.